FIGS. 12(a) and 12(b) show a slide assist mechanism of Patent Document 1. In the example, a main body is disposed to freely slide a sliding door; a projection body 9 which is an operation member is provided in the sliding door; and the sliding door is drawn in through the projection body 9 by a draw-in unit which is an essential portion of the slide assist mechanism provided in the main body. The draw-in unit comprises a case 1 attached to the main body; sliders 2A and 2B disposed freely slidably in the case 1; latches 5 and 5 rotatably supported through a shaft 8 relative to each slider; and urging devices 3. The projection body 9 is provided to project on an upper end surface of the sliding door.
Here, the case 1 is required to be slender and also thin due to a relation wherein the case 1 is disposed along a guide rail on the main body side. Also, each slider 2A and 2B, and the latch 5 are disposed so as to be stabilized and excellent due to the following structure relative to the case 1. Specifically, each projected portion 22 provided on upper and lower surfaces is fitted in guide grooves 12b and 16b provided on the upper and lower surfaces of the case 1, and each slider slides while the slider is guided by a guide device on upper and lower sides. Also, each latch 5 slides while each projection 52 provided on the upper and lower surfaces is being guided by guide grooves 14 and 19 provided on the upper and lower surfaces of the case 1. Each of guide grooves 14 and 19 respectively comprises a straight-line groove 14a and 19a parallel to the guide groove 12b and 16b; and an approximately L-shaped locking groove 14b and 19b provided on both sides of the straight-line groove 14a and 19a. 
In the aforementioned slide assist mechanism, both-side latches 5 in FIG. 12(a) and the right-side latch 5 in FIG. 12(b) are in a standby position. In the standby position, the up and down projections 52 are locked in the corresponding locking grooves 14b and 19b, so that a position of the latch 5 is controlled against an urging force accumulated in the urging devices 3 together with the slider 2A. Then, from the state in FIG. 12(a), when the sliding door, which is in an open position on the left side which is not shown in the figures, is operated to slide from an opening direction to a closing direction, the projection body 9 hits an inner surface of a hook portion 50 of the latch 5 of the draw-in unit wherein the projection body 9 corresponds, so that the latch 5 is rotated due to stress thereof so as to be switched from the standby position to a draw-in position as shown on the left side of FIG. 12(b). In the draw-in position, in a state wherein the latch 5 holds the projection body 9 inside the hook portion, the up and down projections 52 enter in the straight-line grooves 14a and 19a from the locking grooves 14b and 19b so as to release the locking. Consequently, the latch 5 and the slider 2A are slid by the urging force accumulated in the urging device 3 so as to automatically switch the sliding door to a closed position through the projection body 9. Also, from the closed position, when the projection body 9 is slid to the left side of the figures together with the latch 5 due to an opening operation of the sliding door, along with this, an urging force is accumulated in the urging device 3. Furthermore, when the sliding door is moved in the opening direction, an urging force is accumulated again so as to switch the latch 5 to the standby position.